Cognica Database Internals
A Unified Data Processing System
A comprehensive academic textbook on database engine architecture, query processing, and distributed systems.
This book provides an in-depth exploration of the Cognica database engine, covering theoretical foundations, implementation details, and practical engineering considerations. From the unified query algebra that bridges relational, document, and full-text search paradigms to the bytecode virtual machine that executes queries, each chapter combines rigorous theory with real-world implementation insights.
Author
Jaepil Jeong (jaepil@cognica.io)
Part I: Foundations
Establishing the theoretical framework for unified data processing
| Chapter | Title | Topics |
|---|---|---|
| 1 | Introduction to Unified Data Processing | Data paradigm fragmentation, unified algebra motivation, system architecture overview |
| 2 | Mathematical Foundations of Query Algebras | Set theory, Boolean algebra, posting lists, algebraic properties |
| 3 | Extending the Algebra to Graph Structures | Graph type system, path expressions, pattern matching, traversal algebra |
| 4 | Query Optimization Theory | Cost models, plan enumeration, join ordering, cardinality estimation |
Part II: Storage Engine
Building the persistent foundation for data management
| Chapter | Title | Topics |
|---|---|---|
| 5 | LSM-Tree Storage Architecture | Memtables, compaction strategies, write amplification, RocksDB integration |
| 6 | Document Storage and Schema Management | Document model, schema inference, flexible typing, collection management |
| 7 | Inverted Index Architecture | Posting lists, skip lists, term dictionaries, clustered term index |
Part III: Query Processing
Transforming SQL into executable plans
| Chapter | Title | Topics |
|---|---|---|
| 8 | SQL Parser and Semantic Analysis | libpg_query, AST construction, name resolution, type checking |
| 9 | Logical Planning and Optimization | Logical operators, equivalence rules, predicate pushdown, join reordering |
| 10 | Physical Planning and Execution Strategies | Physical operators, access path selection, parallel execution, plan caching |
Part IV: Graph Query Processing
From property graphs to Cypher-over-SQL
| Chapter | Title | Topics |
|---|---|---|
| 11 | Graph Storage and Operations | Property graph model, dual-collection storage, traversal algorithms, adjacency cache |
| 12 | Cypher Query Language | Cypher lexer/parser, AST, Cypher-to-SQL rewriting, recursive CTE path translation |
Part V: Execution Engine
The heart of query evaluation
| Chapter | Title | Topics |
|---|---|---|
| 13 | CVM Architecture | Bytecode VM design, register allocation, opcode dispatch, stack management |
| 14 | CVM Compilation Pipeline | IR generation, lowering passes, optimization phases, code generation |
| 15 | Vectorized Execution | SIMD operations, batch processing, columnar evaluation, filter pushdown |
| 16 | Copy-and-Patch JIT Compilation | Stencil-based JIT, runtime code generation, hot path optimization |
| 17 | Zero-Copy JOIN Implementation | Composite rows, reference semantics, memory efficiency, JOIN algorithms |
Part VI: Similarity Search and Ranking
Bridging structured and unstructured data retrieval
| Chapter | Title | Topics |
|---|---|---|
| 18 | Text Analysis Pipeline | Tokenization, normalization, stemming, stopwords, ICU integration |
| 19 | BM25 Scoring | TF-IDF, BM25 formula, IDF computation, term frequency saturation, numerical stability |
| 20 | Bayesian BM25 and Probabilistic Calibration | Sigmoid likelihood, composite prior, base rate prior, three-term decomposition, WAND compatibility |
| 21 | Vector Search and HNSW Index | Dense embeddings, ANN search, HNSW algorithm, distance metrics, quantization |
| 22 | Vector Score Calibration | Likelihood ratio calibration, cross-modal estimation, index-aware statistics, unified fusion |
| 23 | From Bayesian Inference to Neural Computation | Conjunction shrinkage, log-odds framework, neural emergence, activation functions, exact pruning |
| 24 | Hybrid Search Architecture | Score fusion, log-odds conjunction, multi-stage retrieval, query composition |
| 25 | Query Evaluation Strategies (WAND/BMW) | Top-K algorithms, early termination, block-max optimization, neural pruning |
Part VII: Distributed Systems
Scaling beyond a single node
| Chapter | Title | Topics |
|---|---|---|
| 26 | Raft Consensus Protocol | Leader election, log replication, safety guarantees, membership changes |
| 27 | Transaction Processing | ACID properties, isolation levels, MVCC, SSI, deadlock detection |
Part VIII: System Integration
Connecting to the outside world
| Chapter | Title | Topics |
|---|---|---|
| 28 | PostgreSQL Wire Protocol | Message formats, authentication, extended query protocol, COPY |
| 29 | External Table Integration | Foreign data wrappers, Arrow Flight SQL, predicate pushdown, federation |
| 30 | Multi-Protocol Service Layer | HTTP REST, Flight SQL, protocol multiplexing |
Part IX: Advanced Topics
Engineering for production excellence
| Chapter | Title | Topics |
|---|---|---|
| 31 | Memory Management | Arena allocation, memory pools, cache hierarchies, OOM handling |
| 32 | Observability and Debugging | Metrics, logging, tracing, profiling, EXPLAIN analysis |
| 33 | Performance Engineering | Benchmarking, bottleneck analysis, tuning strategies, capacity planning |
| 34 | Context-Isolated Architecture | ServerContext, singleton removal, bridge patterns, multi-tenancy foundations |
Appendices
Reference materials for implementation and deployment
| Appendix | Title | Contents |
|---|---|---|
| A | CVM Opcode Reference | Complete opcode listing, instruction formats, type system, built-in functions |
| B | SQL Compatibility Reference | Supported statements, data types, operators, functions, PostgreSQL compatibility |
| C | Configuration Reference | All configuration options with types, defaults, and tuning guidelines |
| D | API Reference | PostgreSQL protocol, Flight SQL, HTTP REST endpoints |
Key Innovations
This book documents several key innovations in the Cognica database engine:
Unified Query Algebra
A mathematical framework that treats posting lists as the universal abstraction, enabling seamless queries across relational, document, full-text search, and graph paradigms.
Cypher-over-SQL Graph Processing
A parse-time Cypher-to-SQL rewriting engine that translates graph pattern matching into standard SQL subquery pipelines, enabling graph queries to benefit from the full SQL optimizer without a separate graph execution engine.
Clustered Term Index
A novel inverted index organization that reduces key count by 62,500x compared to traditional term-per-key approaches, dramatically improving write performance.
Cognica Virtual Machine (CVM)
A 256+ opcode bytecode interpreter with computed-goto dispatch, achieving near-native performance for interpreted query execution.
Copy-and-Patch JIT
A stencil-based JIT compilation technique that provides 2-5x speedup for hot query paths with minimal compilation overhead.
Zero-Copy JOINs
Composite row representation that eliminates data copying during JOIN operations, reducing memory pressure and improving cache efficiency.
Bayesian BM25 and Probabilistic Calibration
A three-term posterior decomposition that transforms unbounded BM25 scores into calibrated probabilities, enabling principled multi-signal fusion with 68-77% calibration error reduction in unsupervised settings.
Vector Score Calibration
Likelihood ratio calibration that transforms vector similarity scores into relevance probabilities using distributional statistics extracted from ANN indexes at zero additional cost.
Neural Emergence from Bayesian Inference
The discovery that combining calibrated probability signals through log-odds conjunction analytically produces the structure of a feedforward neural network — reversing the conventional direction of explanation in neural network theory.
WAND/BMW Query Evaluation
Block-max weighted AND algorithms achieving 50-88% document skip rates for top-K retrieval, with proven exact neural pruning guarantees.
Reading Paths
For Database Developers
Start with Part I for theoretical foundations, then proceed through Parts II-V for core implementation details. Appendix A is essential for CVM development.
For Application Developers
Focus on Chapters 8 (SQL Parser), 12 (Cypher), 28 (PostgreSQL Protocol), and 30 (Multi-Protocol Layer). Appendices B and D provide API references.
For Graph Database Developers
Chapter 3 provides the theoretical graph algebra, Chapter 11 covers storage and traversal algorithms, and Chapter 12 details the Cypher-to-SQL rewriting pipeline.
For Operations Engineers
Chapters 31-33 cover production concerns. Appendix C provides comprehensive configuration documentation.
For Researchers
Part I establishes the theoretical framework. Chapters 19-25 cover state-of-the-art information retrieval techniques, including the probabilistic calibration trilogy (Chapters 20, 22, 23) that connects information retrieval to neural computation.
Version Information
- Cognica Version: 1.0
- Last Updated: March 2026
- Total Chapters: 34
- Total Appendices: 4
Copyright 2023-2026 Cognica, Inc. All rights reserved.